Empathy and prosocial development are studied in a sample of monozygotic and dizygotic twins. This is part of a larger longitudinal collaborative investigation based in Colorado of twins studied from late infancy through 7 years of age. Children and their mothers are observed in structured and naturalistic situations in the home and in the laboratory. Maternal observational reports are also obtained. One goal of this research is to assess genetic and environmental factors that influence normative patterns of empathic and prosocial development. A second purpose is to examine whether the early presence of empathic concern for others is an indicator of social-emotional competence that predicts fewer behavior problems, particularly externalizing problems later in development. One recent report from this project focuses on parent and child characteristics that predict changes in children's levels of empathy from 14 to 20 months. Several predictive parent and child characteristics have been identified. Low levels of maternal warmth and less positive family adaptation at 14 months, for example, were associated with a significant drop in children's empathy over time, particularly for girls. To date, empathy and prosocial behavior in the first three years of life has not been associated with less aggression and other externalizing problems by the time these children reach the age of 5 years.